A shaft sealing device is provided around a rotating shaft of a rotating machine such as a gas turbine or a steam turbine so as to reduce the amount of leakage of a working fluid flowing from a high pressure side to a low pressure side. PTL 1 discloses an example of the shaft sealing device.
The shaft sealing device includes a sealing body formed of a large number of thin plate-like sealing pieces. In the shaft sealing device, a large number of the thin plate-like sealing pieces are stacked in a circumferential direction of a rotating shaft in a state where a thickness direction of the thin plate-like sealing pieces is coincident with the circumferential direction. Each of the thin plate-like sealing pieces is disposed in an inclined manner such that a radially inner end of the thin plate-like sealing piece is further rotated in a rotation direction of the rotating shaft than a radially outer end thereof.
In the shaft sealing device, the radially inner end of each of the thin plate-like sealing pieces is a free end. The free end comes into contact with the rotating shaft when the rotation shaft is stopped. In contrast, when the rotating shaft rotates, a lifting force which lifts the free end from an outer circumferential surface of the rotating shaft occurs on a free end side of each of the thin plate-like sealing pieces due to dynamic pressure effects caused by the rotation of the rotating shaft. In the shaft sealing device, when a working fluid flows between the thin plate-like sealing pieces from a high pressure region positioned on one side in an axial direction in which the rotating shaft extends to a low pressure region, the working fluid flows away from the rotating shaft, that is, flows to the outside in a radial direction, while flowing to the low pressure region. For this reason, due to this flow, a pressure distribution is formed such that the thin plate-like sealing pieces are lifted, and a lifting force occurs on the free end side of the thin plate-like sealing pieces.
As such, when the rotating shaft rotates, the free end of each of the thin plate-like sealing pieces is lifted from the rotating shaft, and does not come into contact with the rotating shaft. For this reason, in the shaft sealing device, wear on the thin plate-like sealing pieces is reduced, and seal life is extended.